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Clinical effect and cost effectiveness of screening for asymptomatic carotid stenosis – A Markov model
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences. (Kärlkirurgi)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Objectives:   Screening for asymptomatic carotid artery stenosis (ACAS) is controversial. The cost-effectiveness of screening depends on screening cost, ACAS prevalence, and the potential stroke reducing effect of best medical treatment (BMT). The aim of the study was to determine the threshold values for these parameters in order for screening for ACAS to be cost-effective.

Material and methods: The clinical effect and cost-effectiveness of ultrasound-screening for ACAS with subsequent initiation of BMT versus not screening, was assessed in a Markov model with a life-time perspective. Key parameters; including stroke risk, all-cause mortality, and costs were based on contemporary published data, population statistics and ongoing screening programs. Prevalence of ACAS and rate of ongoing BMT was based on data from a population recently screened for ACAS. Minimum required stroke-risk reduction from BMT, incremental cost-efficiency ratio (ICER), absolute risk reduction for stroke (ARR), number needed to screen (NNS) were calculated. 

Results: Screening was cost-effective at an ICER of €5744 per incremental quality adjusted life-year (QALY) gained. ARR was 135 per 100000 screened, NNS was 741 and QALYs gained were 6700 per 100000 invited. At a willingness-to-pay (WTP) threshold of €50,000 per QALY the minimum required stroke risk reduction from BMT was 22%. The assumed degree of stroke risk reduction was the most important determinant of cost-efficiency.  

Conclusion: A moderate (22%) reduction in the risk of stroke from BMT was required for an ACAS screening strategy to be cost-effective at WTP of €50,000/QALY. Targeting populations with higher prevalence of ACAS could improve cost-efficiency.

Keyword [en]
cost-eefectiveness, carotid stenosis, screening, preventive treatment
National Category
Medical and Health Sciences
Research subject
Surgery
Identifiers
URN: urn:nbn:se:uu:diva-328785OAI: oai:DiVA.org:uu-328785DiVA: diva2:1137658
Projects
Screening for asymptomatic carotid atherosclerosis
Available from: 2017-08-31 Created: 2017-08-31 Last updated: 2017-08-31
In thesis
1. Screening for asymptomatic carotid atherosclerosis
Open this publication in new window or tab >>Screening for asymptomatic carotid atherosclerosis
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ischemic stroke is the most common cause of handicap in adults and the third most common cause of death in Sweden. Internal carotid artery atherosclerosis is an important cause and accounts for 20% of ischemic strokes. Screening for carotid atherosclerosis has been debated over the past two decades.

The aims of this thesis were (I) to study the prevalence of and risk factors associated with carotid artery atherosclerosis among 65 year old men, (II) to evaluate a simplified ultrasound protocol (the grayscale/mosaic method) for the exclusion of significant carotid artery stenosis for screening purpose, (III) to evaluate the required effect of primary preventive therapy in reducing risk of stroke among patients with asymptomatic carotid disease in order for screening to be cost-effective and (IV) to study natural history of carotid atherosclerosis and outcome five years after screening in 65-year old men.

The prevalence of atherosclerotic plaques was high (25%), while the prevalence of >50% stenosis was relatively low (2.0%). Smoking, hypertension, diabetes mellitus and coronary artery disease were independent risk factors and individuals with several risk factors had a higher prevalence of stenosis. Most of those at risk were not on any preventive medication. A simplified grayscale/mosaic method was found to have a high negative predictive value for significant carotid stenosis. The minimum stroke risk reduction effect required for preventive intervention to be cost effective was 22%. Carotid atherosclerotic plaque and stenosis 50-79% has a relatively benign development during five years if treated with BMT and risk factor adjustment. Very few progressed to symptomatic disease. More severe stenosis (80-99%) had higher rate of neurological events, and may benefit from additional intervention.

In conclusion, prevalence of silent atherosclerotic disease in carotid arteries was common among 65-year-old men. Most of those at risk had no secondary prevention. There is a simple DUS method that could be used for screening purpose. Screening for carotid disease is only cost-effective if the preventive strategy lowers the risk of stroke by 22%. Men with plaques and moderate stenosis have a good prognosis, but among those with severe stenosis there is a need for further intervention.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 77 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1367
Keyword
Carotid stenosis, carotid atherosclerosis, screening, cost-effectiveness, natural history, carotid ultrasound
National Category
Medical and Health Sciences
Research subject
Surgery
Identifiers
urn:nbn:se:uu:diva-328803 (URN)978-91-513-0060-3 (ISBN)
Public defence
2017-10-21, Auditorium Minus, Museum Gustavianum, Akademig. 3, Uppsala, 13:00 (English)
Opponent
Supervisors
Projects
Screening for asymptomatic carotid atherosclerosis
Available from: 2017-09-29 Created: 2017-08-31 Last updated: 2017-10-18

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